The present invention relates to catalyst supports in catalytic converters for purifying exhaust gases, and more particularly to shaping at least one of an inlet face and an outlet face of a ceramic catalyst support, wherein the inlet and outlet faces can include a conical or frusto-conical surface.
Early exhaust gas purifying systems included a cylindrically shaped catalyst coated honeycomb substrate having a flat inlet face. Although this conventional system effectively converted pollutants into non-toxic gases, the design tended to exhibit non-uniform flow distribution. Specifically, the high velocity exhaust gases which were emitted from a relatively small diameter exhaust pipe of an internal combustion engine did not significantly diffuse when passing from the exhaust pipe into the larger diameter casing in which the catalyst substrate was located. As a result, a larger portion of the high velocity exhaust gas tended to flow through the center of the honeycomb structure than through the peripheral portion. As a result of this non-uniform flow distribution of exhaust gases through the center, these catalytic converter systems exhibited a loss of conversion efficiency, as well as deactivation of the converter in the region of highest flow velocity. In addition, the non-uniform flow distribution tended to result in a higher pressure drop across the catalyst structure, which in turn results in decreased engine performance.
A variety of attempts have been made to increase the efficiency of the catalytic converter structure. These attempts have included altering the expansion angle between the inlet and the casing. However, the resulting flow still creates non-uniform flow distribution and less than optimum conversion efficiency.
Therefore, a need exists for a catalyst substrate that can enhance uniform gas flow through the substrate and hence the catalytic converter. The need also exists for a catalyst substrate that can provide greater surface area without requiring increased casing volume. The further need exists for forming a catalyst substrate by an economically acceptable process, wherein the resulting substrate can be formed to match the profile of a desired casing or can. The need further exists for a method and apparatus for manufacturing substrates that can have a shaped inlet and outlet face.
The present invention includes an apparatus for shaping a face of a catalyst substrate. The face can be an inlet face or an outlet face, and can be shaped to include a conical or frusto-conical surface. The present system provides for the formation of a monolithic ceramic catalyst substrate having at least one of the inlet face or the outlet face defined by a conical or frusto-conical surface. The present invention can shape the face of a green, dried, calcined or fired ceramic substrate. By shaping at least one of the inlet or outlet faces, a greater volume of substrate can be enclosed in industry accepted casing volumes. Further, the present apparatus can be employed to shape a substrate that can be any of a variety of materials to support a broad spectrum of catalysts.
The apparatus includes a grinding head rotatable about a grinding axis, wherein the grinding axis is translatable about an orbital path. The orbital path can be selectively controlled in response to the cross sectional profile of the given substrate to provide a shaped face of the substrate. The apparatus can include a sensing station and a controller to allow for customization of the face. Thus, the present invention can form a face having a curvilinear surface as well as a face having a faceted surface.